1. Field of the Invention
The present invention relates to a solar cell, and particularly, to a method for manufacturing solar cell by processing surface of silicon substrate for solar cell, and solar cell manufactured by the same method.
2. Background of the Invention
A solar cell indicates a cell capable of generating electromotive force by using photo-electromotive effect, one of photoelectric effects.
The solar cell may be classified into a silicon-based solar cell, a compound semiconductor solar cell, a compound or lamination-type solar cell according to material of substrate. Here, the silicon-based solar cell may be categorized into a crystalline silicon solar cell such as a monocrystalline silicon and a multicrystalline silicon, and an amorphous silicon solar cell.
The efficiency of solar cell is determined by a plurality of factors such as reflectivity of a substrate, and is maximized by minimizing reflectivity on a light receiving surface.
In the field of a crystalline silicon solar cell having relatively low fabrication costs, various methods for minimizing reflectivity in order to enhance efficiency for the solar cell are being proposed.
A solar cell (device) manufactured by crystalline silicon, especially, multicrystalline silicon undergoes the following steps.
Firstly, a substrate is manufactured by slicing crystalline silicon ingot.
The sliced substrate undergoes protrusion forming step so as to reduce reflectivity on a light receiving surface and so as to remove damages occurred on the surface of the substrate during the slicing process. As a result, a plurality of protrusions are formed on the light receiving surface of the substrate.
The substrate having undergone the protrusion forming step undergoes impurity doping and diffusion processes, thereby having semiconductor structure. After forming anti-reflection film on the light receiving surface, electrodes are formed on the light receiving surface and the bottom surface. As a result, a solar cell is manufactured.
In case of performing the protrusion forming step by wet-etching process, not only the light receiving surface but also the bottom surface of the substrate are etched. This may cause the bottom surface of the substrate to have undesirable protrusions.
In order to solve the problem, in case of performing the protrusion forming step by wet-etching process, a mask for preventing formation of protrusions is formed on the bottom of the substrate.
However, the mask has to be removed after forming the mask on the bottom surface of the substrate. This may cause the entire processes to be complicated, and cause the manufacturing costs to be increased.